INTERMEDIATES FOR THE SYNTHESIS OF LINEAR-CHAINS OF 1,2 4,5-FUSED CYCLOHEXA-1,4-DIENE RINGS AND BELTENES BY REPEATED DIELS-ALDER REACTIONS/

A synthetic strategy for the preparation of chains of 1,2:4,5-fused cy clohexa-1,4-diene rings, both linear and cyclic (beltenes), based on t he repetitive Diels-Alder cycloaddition of p-benzoquinone with a tetra methylene- ethane synthon (3,4-dimethylenetetrahydrothiophene 1,1-diox ide) is described. This route has been developed to yield xahydro-1H,3 H-anthracene-[2,3-c:6,7-c']dithiophene 2,2,8,8-tetraoxide 16, a potent ial precursor of a tricyclic doubly-exocyclic diene, and loxy)-1,4,5,6 ,11,12-hexahydronaphthacene-1,4-dione 22, a potential precursor for th e double dienophile ,6,11,12-tetrahydronaphthacene-1,4,7,10-diquinone. but the generation of these Diels-Alder components and their combinat ion to form a [9]-beltene derivative has not been accomplished. The sy nthesis of linear derivatives has proceeded as far as a protected hept acyclic derivative. ylsilyloxy)-5,6,8,9,14,15,17,18-octahydroheptacene 25. The H-1 NMR spectrum of this compound is unexpectedly temperature dependent.